build mode issue

hi! I’m having a problem regarding an unremovable 2nd floor that doesn’t seem to be following the shape of any of the rooms. I can’t figure out how to remove it. I’ve done building under or above it but all it does is extend the unremovable flooring. Even when I try to remove it, it makes the sound that I’ve deleted it but it’s still there. I’m not really sure what to do and it’s been bothering me.